1. Field of the Invention
This invention relates to a method of recovering high purity columbium oxide from pyrochlore ores. More specifically, it deals with the obtaining of columbium oxide from barium-rich and calcium-rich pyrochlore ores.
2. Description of the Prior Art
How to obtain columbium and tantalum values from pyrochlore ores is well known. These processes are usually drawn to the production of ferro-columbium, which is subsequently used in that state for such purposes as additions to metal alloys. It is also possible to obtain columbium oxide values by a caustic fusion process from certain pyrochlore ores found in Canada. These oxides, however, are not easily available in any measure of purity from other pyrochlore ores of a barium-rich nature, such as those found in Brazil. Although the metal oxides are obtainable in relatively large yields from those ores, they are of a purity of about 80-85%, which is unacceptable for most purposes. By bariumrich pyrochlore ores, we mean those whose barium content is from 2 to 20% by weight, and whose calcium content is lower, generally less than 2% by weight. Calcium rich pyrochlore ores usually have greater than 2% and as much as 20% calcium content by weight. The impurities consist mainly of barium and calcium, along with smaller amounts of titanium, zirconium, rare earths, uranium, and thorium. These impurities, which for the main part are calcium and barium, are so tied up with the columbium oxide that the product produced is unsatisfactory as it exists for most uses.
In view of the fact that columbium is becoming a more important refractory metal and is being used for such items as jet engine exhausts, high temperature alloys, rocket nozzles, and superconductors, it is now in industry's interest to be able to produce high purity columbium oxide in increasingly larger amounts. In view of the above, and in light of the fact that there are large sources of pyrochlore ore having a high content of barium, there is a need to find a process to produce high purity columbium oxide from this type of ore.